Fan having annular frustro-conical diffuser space



Feb. 14, 1967 F. K. BAYLESS FAN HAVING ANNULAR FRUSTRO-CONICAL DIFFUSER SPACE Filed April 28, 1965 4 Sheets-Sheet 1 INVEN TOR.

BAYLESS' FRANK HlS ATTORNEY Feb. 14, 1967 F. K. BAYLESS 3,303,996

FAN HAVING ANNULAR FRUSTRO--CONICAL DIFFUSER SPACE Filed April 28, 1965 4 Sheets-Sheet 2 PEG. 3

1N VENTL )R. FRANK K. BAY LESS HIS ATTORNEY Feb. 14, 1967 F. K. BAYLESS 3,303,996

FAN HAVING ANNULAR FRUSTRO-CONICAL DIFFUSER SPACE 4 Sheets-Sheet 5 Filed April 28, 1965 IN V) AT TOR N EY HIS 1967 F. K. BAYLESS FAN HAVING ANNULAR FRUSTRO-CONIGAL DIFFUSER SPACE Filed A ril 28, 1965 4 Sheets-Sheet 4 mt; 5x01 512 no mtz: mi

FRANK K. BAYLEss 4. AT TO R NEY FLOW IN UNITS OF VOLUME OF AQR PER UNiT OF ELAPSED THWE, F. M. BY

HIS

United States Patent Delaware Filed Apr. 28, 1965, Ser. No. 451,535 Claims. (Cl. 230-430) My invention relates, in general, to motor-fan units, such as those used in vacuum cleaners; and, more particularly, to a fan unit having an annular frustro-conical diffuser space through which air is exhausted from the fan.

Motor-fan units,'whether they be used in vacuum cleaning applications or otherwise applied, may be classified into three general types: (1) the direct-flow type; (2) the reverse-flow type; and (3) the type wherein an airstream separate and distinct from that produced by the fan is used for cooling the motor.

One example of the third mentioned type, wherein separate airstream motor cooling is used, is described and illustrated in US. Patent No. 2,822,122, granted February 4, 1958, to J. D. Cole.

In the reverse-flow motor-fan unit, as arranged in a vacuum cleaner tank unit, filtered air at a relatively low temperature passes through the dust bag and flows, first, over the motor to cool it. Then it flows through the fan where its temperature is raised considerably before it is exhausted from the fan. One example of the reverseflow type of unit is described and illustrated in U.S. Patent No. 3,096,929, granted July 9, 1963 to A. L. Sebok et 211.

By way of contrast with the reverse-flow type, in a direct-flow motor-fan unit the filtered air leaves the dust bag and, first, enters the fan where it is raised to a relatively high temperature. Then, this high temperature air is passed over the motor. One example of the directflow type of unit is described and illustrated in U.S. Patent No. 2,915,237, granted December 1, 1959, to F. L. Galiulo et al.

In the third mentioned type of fan unit, a separate airstream is used for cooling the motor.

Accordingly, one object of my invention is to provide a diffuser of novel configuration for use in any of the aforementioned motor-fan unit types in order to improve the suction cleaning airstream performance; 1.e., to provide increased fan suction, or vacuum, over the entire airflow range of the cleaning air or, conversely, to i provide increased flow of the cleaning air over the entire range of vacuum.

Another object of my invention is to provide an economical relatively simple diffuser construction having a minimal number of parts and being adapted for easy assembly with a fan unit.

Another object of my invention is to provide a reverseflow motor-fan unit which has my novel diffuser incorporated therein in order to increase the vacuum over the entire airflow range of the fan unit, or, conversely, to increase the airflow over the entire range of vacuum produced by the fan.

An important feature, among others, of my invention resides in the use of a novel diffuser configuration for efficiently converting a substantial amount of the velocity energy of the air being exhausted from a fan into pressure energy.

According to one embodiment of my invention, I provide a rnulti-stage centrifugal fan, or blower, with wall members which form a generally annular space that concentrically encompasses the last stage impeller of the fan. These wall members also form an annular frustroconical space which is contiguous with the annular space and extends axially with respect thereto. Thus, the high velocity air propelled into the annular space by the last stage impeller diffuses through the annular space and then into and through the progressively enlarging crosssectional area of the annular fru-stro-conical space.

Other objects and features of my invention will be apparent from the following description when considered in conjunction with the accompanying drawings in which:

FIG. 1 is a longitudinal, cross-section, showing a reverse-flow motor fan unit situated in the tank unit of a vacuum cleaner and incorporating one embodiment of the diffuser according to my invention;

FIG. 2 is a somewhat enlarged partial section of FIG. 1 showing my diffuser in greater detail;

FIG. 3 is a somewhat diagrammatic view of my diffuser showing various geometrical relationships thereof and a somewhat idealized representation of the airflow therethrough;

FIG. 4 is a diagrammatic view similar to FIG. 3 but showing a section of my diffuser as being straight, rather than arcuate, so that the various geometrical relationships thereof and the idealized airflow representation may be more clearly shown for purposes of explanation;

FIG. 5 is a partial longitudinal cross-section similar to that shown in FIG. 1, but showing a second embodi ment of my diffuser incorporated in a reverse-flow motorfan unit which is situated in a vacuum cleaner tank unit:

FIG. 6 is a partial cross-section view as viewed along the line 66 in FIG. 5;

FIG. 7 is a graphical representation showing the air performance of a reverse-flow motor-fan unit having a diffuser according to my invention; and,

FIG. 8 is another graphical representation showing the electrical performance of the reverse-flow fan unit having a diffuser according to my invention.

In FIG. 1 a motor-fan unit having a diffuser according to the first embodiment of my invention is shown mounted within a tank 10 of a tank-type or canister-type vacuum cleaner, the unit being of the reverse fiow type. A dust bag compartment 12 having a plurality of holes 13 therethrough is also mounted within the tank 10 and a dust bag 14 is situated in the compartment 12.

The motor-fan unit is comprised of an electric motor 16 and a centrifugal fan 18 which is driven by the motor. The motor and fan are located downstream of the dust bag 14 so that filtered airstreams, indicated by the arrows A, emanating from the dust bag can pass over the motor 16 to cool it before the airstreams enter the fan 18.

The motor 16 may be a conventional series wound universal motor including a wound armature 20 on an armature shaft 21 which is journaled for rotation in the two bearing members 22 and 23. Surrounding the armature 20 is a laminated stator 19 which includes two opposing pole pieces 24. A field winding encompasses each pole piece 24. One end of the armature shaft 21 is provided with a commutator 26 which is electrically energized through a pair of carbon brush units 17. The motor 16 also includes two stationary support frames 27 and 28 which when coupled together by means of bolts 29 support the stator 19 and armature 20. The support frame 27 includes ribs 30 between which there are defined openings so that the airstreams A can pass over the various parts of the motor to cool it. As indicated, the airstreams A pass over the armature 20, stator 19 and field winding 25. In addition, the support frame 27 serves as a support for the bearing member 23 and for the brush units 17. The support member 28 has a cup-like shape and is open at one end, the other end thereof being partly closed and carries the bearing member 22. At the partly closed end of the support frame 28 there is formed a number of radial spokes 31, or rib members and between these adjacent spokes 31 openings are provided so that airstreams A can pass through, as indicated in FIG. 1, into the fan unit 18. Support-frames 27 and 28 may be fashioned from aluminum or the like; for example, cast aluminum is one of a number of materials which are suitable.

Fastened by means of rivets 32 to the outside surface of support frame 28 at the partly closed end thereof is a stationary cup-like housing 33 which may also be fashioned from aluminum. At one end of this housing 33 there is formed anoutwardly turned annular flange 34 and in about three or four places on this flange there are provided large diameter holes 35, through which bolts 36 pass for the purpose of securing the housing 33 to a bulkhead 37, which bulkhead is secured to the inside surface of the tank 10, as by welding. An annular rubber gasket 38 is also provided to help secure these aforementioned members together so that vibrations may be damped. In the center of the partly closed end of the support frame 28 there is a circular hole within which the inner bearing race 39, ball bearings 40 and an outer bearing race 41 are situated. The armature shaft 21 passes through a hole provided in the center of the inner hearing race 39. Secured to the support frame 28 by means of screws (not shown) are the two centrally apertured stationary bearing shields 42 and 43. As shown'the diameter of the central aperture of these shields 42 and 43 is sufficiently large so that the shields will not interfere with rotation of the armature shaft 21 or with any of the other elements, hereinafter identified, which rotate together with the armature shaft 21. The spaces between the two bearing races 39 and 41 .and between the two shields 42 and 43 are filled with a suitable lubricant, e.g.,

grease. Y

Fitted over the outside surface of the housing 33 and fastened thereto is another stationary cup-like housing 44. The housing 44 which may be formed from sheet aluminum or the like extends for a substantial distance in an axial direction beyond the end of the housing 33. Within the space defined between the outer end wall of housing 33 and the interior end wall of the housing 44 there is located a first stage centrifugal impeller 45 and a first stage stationary diffuser 46.

At one end of the cup-like housing 44 there is provided an opening 47 through which 'airstreams A can flow into a second or final stage centrifugal impeller 48. Within the cup-like housing 44 and arranged parallel to an inside wall surface thereof there is a centrally apertured circular disc 49. Between the housing 44 and the disc 49 there is situated a plurality of spaced-apart spiral-like vanes 50. The vanes 50* are radially arranged in the space between a Wall of housing 44 and the disc 49. Each vane 50 has projecting cars such as the ear 51. These cars 51 extend through accommodating holes in the housing 44 and in the disc 49 and are bent over onto the outside surfaces of the housing and the disc. To ensure a positive connection to the housing 44 and to the disc 49 which also encompasses the shaft 21.

the bent over cars 51 of the vanes 50 may be spot welded thereto. As may be seen in FIG. 1 the central aperture in the disc 49 has a diameter large enough to allow the armature shaft 21 and the other elements coupled therewith to rotate freely without interfering with the disc 49. Thus, the first stage diffuser 46 is comprised of the stationary end wall of housing 44, the disc 49 and the vanes 50 situated therebetween.

The first stage centrifugal impeller 45 is located between the wall member 33 and the stationary diffuser 46, as shown in FIG. 1. The impeller 45 is comprised of two spaced-apart circular discs 52 and 53 and spiral-like radially arranged vanes 54 connected therebetween. Each vane 54 includes a plurality of ears, such as the ear 55, which protrude through accommodating holes in the discs 52 and 53. These ears 55 are bent over and may be spot welded to the outside surfaces of the discs. As shown, the disc 52 has a large diameter central aperture 56 which admits airstreams A into the impeller 45.

The second or last stage impeller 48 is comprised of two spaced-apart circular discs 57 and 58 :and radially arranged spiral-like vanes 59 connected therebetween. These vanes 59 are regularly spaced-apart between the discs 57 and 58 and each vane includes a plurality of ears 60 which protrude through accommodating holes in the discs 57 and 58 and are bent over and may be spot welded to-the outside surfaces of these discs. As shown the disc 57 has a large diameter central aperture 61 to admit airstreams A into the final stage impeller 48.

The armature shaft 21 has an enlarged section 62 having a diameter greater than the remainder of the shaft 21. At the juncture of the enlarged section 62 and the smaller diameter portion of the armature shaft there is defined an annular shoulder 62 against which one end of the inner bearing race 39 is in contact and situated next to the opposite end of the bearing race 39 is a flanged cylindrical body 64. One end of this body 64 is in contact with the end of the bearing 39 and the flanged portion of the body 64 is in contact with the face of disc 53. In contact with the opposite face of the disc 53 there is the centrally wapertured washer 65 which encompasses the armature shaft 21. Next to the washer 65 and in contact therewith is a centrally apertured cylindrical body 66 which also encompasses the armature shaft 21. Situated between the opposite end of the cylindrical body 66 and theface of the disc 58 is another centrally apertured washer 67 In contact with the opposite face of disc 58 is another centrally apertured washer 68 which also encompasses the armature shaft 21. The end of the armature shaft 21 is externially threaded and it receives an internally threaded nut 69 which is tightened so as to bear with considerable force against the face of the washer 68. The force exerted by nut 69 is transmitted to the annular shoulder 63 through the washer 68, disc 58, washer 67, cylindrical body 66, washer 65, disc 53, flanged body 64 and the inner bearing race 39. Thus, all of the aforementioned parts between the shoulder 63 and the nut 69 and including the nut 69 rotate together with the armature shaft 21 due to the high pressure contact therebetween. Also since the discs 52 and 57 are rigidly securedto the discs 53 land 58 through the vanes 54 and 59 respectively in the manner hereinbefore set forth, the first and second stage impellers 45 and 48 defined by these vanes and discs rotate together with the armature shaft 21.

A dish-like wall member or cup 70 formed in a somewhat frustro-conical shape from suitable sheet metal, such as aluminum, is secured to the outside of the housing 44 by means of the evenly spaced brackets 71 and the sheet metal screws 72. The mounting brackets 71 are spot welded to the inside surface of the wall member 70 and the sheet metal screws 72 are threaded through the brackets 71 land the Walls of the housings 33 and 44, as indicated atFIG. 1, so that the wall member 70 is maintained in a spaced relationship relative to the housing 44.

As shown in FIGS. 2 and 3 the volumetric space between the tip of the final stage impeller wheel 48 and the inside surface of the wall member 70 which is above the tip of the wheel 48 is somewhat annular. This space would be perfectly annular except for the curvature of that portion of the wall member 70 which is above the tip of the impeller wheel 48. Contiguous with the aforesaid annular space and extending axially therefrom is the annular frustro-conical diffuser space provided in accordance with my invention, which diffuser space extends longitudinally from the line L1 to the line L2 (see FIG. 2) and is bounded by the inside surface of the wall member 70 and the outside surface of the housing 44. As shown in FIG. 2 the wall member 70 is outwardly flared at an angle B relative to the wall surface of the housing 44.

Tests, hereinafter disucssed in detail with reference to FIGS. 7 and 8, were conducted to determine relative performances of a reverse-flow motor-fan unit having, in accordance with my invention, an annular frustroconical diffuser and a like motor-fan unit having a conventional prior art annular cylindrical diffuser. These tests showed that the motor-fan unit incorporating the aforesaid annular frustro-conical diffuser produced a higher suction of vacuum over its entire airflow range than the comparable motor-fan unit employing the conventional prior art diffuser.

While it is not fully understood why the motor-fan unit employing my annular frustro-conical diffuser performs better than the prior art motor-fan units the following explanation, based on FIGS. 3 and 4, seems to account for the improved performance. However, I do not wish to be bound by such explanation.

In FIGS. 3 and 4 there exists the following relationship between the angles B, C and D.

tan D=sin C'tan B In the above equation B is the angle at which the wall member 70 is disposed relative to the housing 44 (see FIG. 2). C is the angle at which airstreams A exit into the diffuser space which is defined between the wall member 70 and the housing 44. The angle C was measured by observing the position which a thread assumed when it was inserted into the annular space above the tip of the final stage impeller wheel 48. The angle D, which is calculated from the above equation, is the diverging angle at which it is believed the airstreams A diffuse into the annular frustro-conical diffuser space.

In one illustrative embodiment of my invention the angle B was set at 17 and the angle C was measured with the aid of a thread to be 20. The angle D was calculated to be 6. For air a diffusion angle of between 6 and 8 is considered to be the range which permits the air to diffuse with the least loss of energy. Thus it seems plausible that the reason for the improved performance of a fan unit embodying my annular frustroconical diffuser is that airstreams can seek an effective diffusion angle of between 6 and 8 which diffusion angle permits the air to convert its velocity energy into pressure energy with the least energy loss.

Another embodiment of my invention is shown in FIGS. 5 and 6. The motor-fan unit shown in these figures is the same as motor-fan unit shown at FIGS. 1 and 2 with the exception that vanes 73 or air guides are added to the outer surface of the wall member 70. As shown in FIGS. 5 and 6, the vanes 73 are evenly spaced circumferentially about the outer surface of the wall member 70. Each vane 73 has an L-shaped cross-section and one leg of each vane is welded to the wall 70.

Three reverse flow motor-fan units were tested and the tests appear in graphic form in FIGS. 7 and 8. Motorfan unit I was provided with a conventional vaneless annular cylindrical diffuser wherein the wall member 70 was maintained parallel to the housing 44 rather than disposed at the angle B as shown in FIG. 2. Motor-fan unit II was provided with an annular frustro-conical diffuser of the kind shown in FIGS. 1 and 2. Motor-fan unit III was provided with the annular frustro-conical diffuser and the vanes 73 as shown in FIGS. 5 and 6. In each of the three motor-fan units the diameter of the fan housing 44 was approximately 5.3 inches. The diameter of the impeller wheels are approximately 4.9 inches and each impeller wheel had an axial length of about 0.3 inch. In motor-fan unit I a constant distance of approximately 0.120 inch was maintained between the wall member and the housing 44. In motor-fan units II and III the throat dimension T indicated in FIG. 2 was maintained at 0.120 inch. In motor-fan units II and III the angle B of the wall member 70 relative to the housing 44 was maintained at 17.

A comparison of the motor-fan units II and III with the motor-fan unit I in FIG. 7 shows that the motorfan units II and II provided a higher suction over the entire airflow range as compared with the suction produced by motor-fan unit I. Further, motor-fan unit III produced an even higher suction over its entire airflow range than motor-fan unit II. Moreover, as appears in FIG. '8 the higher suction produced by motor-fan units II and III was achieved at but a relatively insignificant increase in input power.

While I have disclosed two more or less specific embodiments of my invention it is to be understood that this has been done for purposes of illustration only. Also, although I have shown my invention in connection with reverse-flow motor blower units, it is equally applicable to direct-flow blowers and to blowers having separate cooling of the motor, and the scope of my invention is to be limited only by the appended claims.

What I claim is:

1. In combination with a centrifugal fan having an impeller wheel which discharges air from its periphery, first wall means forming an annular frustro-conical diffuser space which has its smaller cross sectional area positioned to receive the air discharging from the periphery of the impeller wheel, second wall means coaxially encompassing said first wall means and forming therewith another diffusion space for guiding the air exiting from the annular frustro-conical diffusion space in a direction which is axially opposite to the axial direction of the air diffusing through said annular frustro-conical space.

2. The combination defined by claim 1 wherein a plurality of vanes are located in the diffusion space defined between the first and second wall means for guiding the air through said diffusion space.

3. In a blower unit, an annular axially extending housing, a centrifugal impeller rotatably mounted within said housing, said housing having an inlet opening located adjacent to the center of said impeller at one end of said housing and having a discharge opening in the opposite end of said housing, a cup member axially spaced from the discharge opening in said housing, a second centrifugal impeller rotatably mounted in said axial space between the cup member and the housing, said cup member having a continuous wall of frustro-conical shape overlapping said housing in spaced relation therewith and extending toward said inlet end with an increasing diameter, the space between said housing and said cup member defining a diffusion chamber for the blower unit with an outlet at the enlarged end of the chamber, and means for supporting said cup shaped member relative to said housing.

4. A blower unit according to claim 3 with the addition of second wall means coaxially surrounding said continuous wall of frustro-conical shape for defining a second annular diffusion chamber therebetween, the outlet of said second diffusion chamber being in a different plane from the outlet of said diffusion chamber defined by said housing and said cup member, the airflow in said first diffusion chamber being directed into said second diffusion chamber.

5. A blower unit according to claim 4 with the addition of a plurality of radially spaced axially extending vanes in said second diffusion chamber.

References Cited by the Examiner UNITED STATES PATENTS 8 2,731,194 1/1956 Kent 230--130 3,011,693 12/1961 Downs et a1. 230-117 8/1965 Wasson et a1. 230-417 FOREIGN PATENTS 701,560 12/1953 Great Britain. DONLEY J. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner. 

1. IN COMBINATION WITH A CENTRIFUGAL FAN HAVING AN IMPELLER WHEEL WHICH DISCHARGES AIR FROM ITS PERIPHERY, FIRST WALL MEANS FORMING AN ANNULAR FRUSTRO-CONICAL DIFFUSER SPACE WHICH HAS ITS SMALLER CROSS SECTIONAL AREA POSITIONED TO RECEIVE THE AIR DISCHARGING FROM THE PERIPHERY OF THE IMPELLER WHEEL, SECOND WALL MEANS COAXIALLY ENCOMPASSING SAID FIRST WALL MEANS AND FORMING THEREWITH ANOTHER DIFFUSION SPACE FOR GUIDING THE AIR EXITING FROM THE ANNULAR FRUSTRO-CONICAL DIFFUSION SPACE IN A DIRECTION WHICH IS AXIALLY OPPOSITE TO THE AXIAL DIRECTION OF THE AIR DIFFUSING THROUGH SAID ANNULAR FRUSTRO-CONICAL SPACE. 